Lecture 8: Tsunamis Flashcards
1
Q
what size earthquake required?
A
hello
- >7.5 with their epicenters underwater
2
Q
low attenuation
A
- attenuation is the loss of energy as it travels longer distances
- energy travels far as has a potential to damage far away from the source
- low attenuation therefore remains high energy even when traveling far from the epicenter
3
Q
what causes them
A
- earthquakes, volcanoes, underwater landslides
4
Q
amplitude
A
- max value measures from the equilibrium
5
Q
period
A
time between two successive crests
- T(s) = 1/f(Hz)
6
Q
frequency
A
- number of waveforms in 1 s
- f(Hz) = 1/T(s)
7
Q
velocity of propagation
A
- v(m/s)
- v = L/T
8
Q
characteristics of wave
A
water of circles decreases with depth
9
Q
shoaling
A
- occurs when waves interact with the seafloor near the shoreline
- interaction starts when depth is less than L/2
- friction slows wave down
- wavelength decreases thus energy is concentrated in a shorter length
- amplitude increases and wave breaks
10
Q
wind caused waves
A
- created by friction between wind and water surfaces
- wind-caused waves confined to first hundred meters of water
- period = 5-20 s
- amplitude = 1-3 meters
- length - 100 m
11
Q
tsunami waves size
A
- in open ocean amplitude is <1m but near shiore 6-15 m
- period = 10-60 minutes
- 2-3 wave is the largest
- length = 100 km
12
Q
pacific tsunami warning center
A
- screen earthquakes
- predicts arrival times at selected coastal communities
- if tsunami is detected authorities evacuate towns
13
Q
bottom pressure recorder
A
- senses pressure changes as tsunami wave passes
- not affected by wind caused waves
14
Q
instruments in tsunami monitoring
A
- data telemetry
- from bottom pressure recorder to buoy then to satellite
15
Q
submarine landslide
A
- earthquake triggered a large submarine landslide on the continental slide
